We currently have a 212-50, however we're quite interested in your 3424. We're not sure however what effect the reduced sample rate will have on our measurements. Is there a way of fudging picoscope software to repoduce a lower sample rate?

Yes you should be able to change the number of samples used in Settings | Options | Advanced. There is a setting for Number of Samples Per Scope Trace, if you lower this then this should have the same effect.